Why does it appear that some users do not see a reduction in their ThreatScore when the score should be reduced by 1/2 in the allotted time-frame?
"ThreatScore Automatic Reduction" is enabled. (Detect > Preferences > General)
Only users with recent activity will have their ThreatScore reduced.
If a dormant of static user is only occasionally used, the ThreatScore could stay low and not be flagged as a high risk user.